Interface apparatuses of this type are used to transmit data from a first domain to a second domain. A common problem in this case is that the first and second domains operate at different clock frequencies. When accessing a memory in the interface apparatus, the problem therefore arises that access operations from the two domains, which operate at different clock frequencies, may occur. The different clock frequencies result in conflicts because, for example, one of the domains writes data before the other domain has read previously stored data.
One known solution in the case of small frequency differences is to use “synchronization registers”. However, the latter can be used only when the frequency difference is minimal.
Another known solution is to switch the clock over between the clock signal for the first domain and that for the second domain. In such a case, the interface apparatus can therefore operate at either one or the other clock frequency. However, such an implementation of the interface is not always satisfactory. One typical use is, for example, in chip cards, which are provided with both contactless and contacted interfaces and are intended to be used simultaneously in both operating modes. By way of example, data are received in contacted fashion and are transmitted in contactless fashion. Correct operation is not always guaranteed in this instance of application.